The stator lamination cores in most of the highpower permanent magnet synchronous machine (PMSM) are axially segmented into a number of substacks by stator radial ventilating ducts so that the effective thermal management of the stator windings can be accomplished. However, these radial cooling ducts will impose certain impacts on electromagnetic characteristics especially in the axial direction, which could potentially lead to inaccurate predictions from conventional twodimensional (2-D) finite element analysis (FEA). Hence, complex three-dimensional (3-D) FEA, which is of high computational intensity, is essential to accurately evaluate the overall effects of
these air ducts. A novel approach based on synthesized 3-D FEA with approximate boundary conditions is proposed in this paper in order to alleviate computational load. The results from the 2-D, proposed synthesized and comprehensive 3-D FEA methods have revealed that the proposed 3-D FEA method can not only deliver more accurate predictions than the conventional 2-D FEA one, but also consume much less computational time than the comprehensive 3-D FEA one.